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Wright State University

1985

Articles 1 - 6 of 6

Full-Text Articles in Physics

Magnetoresistance Method To Determine Gaas And Alxga1-Xas Mobilities In Alxga1-Xas/Gaas Modulation-Doped Field-Effect Transistor Structures, David C. Look, George B. Norris, W. Kopp, T. Henderson, H. Morkoç Aug 1985

Magnetoresistance Method To Determine Gaas And Alxga1-Xas Mobilities In Alxga1-Xas/Gaas Modulation-Doped Field-Effect Transistor Structures, David C. Look, George B. Norris, W. Kopp, T. Henderson, H. Morkoç

Physics Faculty Publications

Charge carrier mobilities are conveniently measured in simple, homostructure field-effect transistors (FET's) by means of the geometric magnetoresistance (GMR) technique. Heterostructure FET's, however, are more complicated because of multiple conducting regions, as well as multiple conducting bands within a given region. We apply a multilayer GMR mobility model to a frequently used heterostructure FET design, namely, the Al0.3Ga0.7As conduction band. In the particular MODFET structure studied here, the lowest GaAs subband mobility ranges from 5.7X103 cm2/Vs at threshold to 6.9X103 cm2/Vs at saturation while Al0.3Ga0.7As mobility …

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Theoretical And Experimental Capacitance-Voltage Behavior Of Al0.3ga0.7as Gaas Modulation-Doped Heterojunctions - Relation Of Conduction-Band Discontinuity To Donor Energy, George B. Norris, David C. Look, W. Kopp, J. Klem, H. Morkoç Aug 1985

Theoretical And Experimental Capacitance-Voltage Behavior Of Al0.3ga0.7as Gaas Modulation-Doped Heterojunctions - Relation Of Conduction-Band Discontinuity To Donor Energy, George B. Norris, David C. Look, W. Kopp, J. Klem, H. Morkoç

Physics Faculty Publications

For the first time, we show that the capacitance-voltage behavior of modulation-doped heterojunctions may be accurately described by a first-principles theory that includes selfconsistent quantum two-dimensional (2-D) electron subbands in the GaAs, numerical solution of Poisson's equation for band bending and space charge in the (Al,Ga) As, and series resistance in the 2-D channel and heterointerface. The excellent agreement found between the theory and measurements on selected high-quality Al0.3Ga0.7 As/GaAs heterojunctions allows accurate determination of the maximum 2-D carrier concentration. From this, we find a strong relationship between the conduction-band discontinuity and donor binding energy, giving offsets. …

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Determining The Temperature-Dependent Characteristic Temperature Of Beryllium From Electrical Resistance Measurements, Thomas W. Listerman, Xiao-Li Zhou May 1985

Determining The Temperature-Dependent Characteristic Temperature Of Beryllium From Electrical Resistance Measurements, Thomas W. Listerman, Xiao-Li Zhou

Thomas Listerman

We have developed an intermediate-level laboratory experiment to determine the temperature- dependent characteristic temperature of beryllium. The apparatus used to measure the resistance of a beryllium wire sample between liquid nitrogen and room temperatures was simple. The characteristic temperatures obtained from these data using the Block-Grüneisen model are in reasonable agreement with literature values obtained from resistivity and heat capacity experiments. The experiment introduced students to cryogenic and computer data analysis techniques and forced them to extend their knowledge of the theory of electrical resistance and of characteristic temperatures.

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Summary Abstract: Capacitance-Voltage Characteristics In Modulation Doped Heterojunction Fets, George B. Norris, David C. Look, W. Koop, J. Klem, H. Morkoç Mar 1985

Summary Abstract: Capacitance-Voltage Characteristics In Modulation Doped Heterojunction Fets, George B. Norris, David C. Look, W. Koop, J. Klem, H. Morkoç

Physics Faculty Publications

No abstract provided.

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Schottky-Barrier Profiling Techniques In Semiconductors - Gate Current And Parasitic Resistance Effects, David C. Look Jan 1985

Schottky-Barrier Profiling Techniques In Semiconductors - Gate Current And Parasitic Resistance Effects, David C. Look

Physics Faculty Publications

The theory for obtaining mobility and carrier concentration profiles by the Hall-effect, magnetoresistance, and capacitance-conductance methods is developed in the relaxation-time approximation. This theory is then applied to semiconductors in which a Schottky barrier is used to control a depletion region. Particular emphasis is given to field-effect transistor structures which are ideally suited for geometric magnetoresistance measurements. A unique feature of the present model is the correction for finite gate (Schottky-barrier) current, which can be very important under forward-gate-bias conditions. The ability to use forward-bias makes the near-surface region more accessible. Also, parasitic resistance effects are treated. We apply these …

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The Vibrational Distribution Of N2+ In The Terrestrial Ionosphere, Jane L. Fox, Alexander Dalgarno Jan 1985

The Vibrational Distribution Of N2+ In The Terrestrial Ionosphere, Jane L. Fox, Alexander Dalgarno

Physics Faculty Publications

The densities and vibrational distributions of N2+ in the X²Σg+, A²Πu, and B²Σu+ states in the daytime terrestrial ionosphere are computed for both low and high solar activity. Altitude profiles of the relative populations of the vibrational levels of N2+X²Σg+ are presented. The fraction of vibrationally excited N2+ varies from 5% at 100 km to 50% at 450 km. Several models are examined in which loss of N2+(v) is enhanced for v > 0 and in …

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